During series production of passenger cars, and particularly during surface treatment with the aid of robots, it is a requirement to be able to paint the car body externally as well as internally without contaminating the freshly painted surface. This means that it must be possible automatically to open and close the doors of the car body, without there being deposited any marks on the freshly painted doors. This problem has hitherto been solved with a robot, which e.g. is programmed to find a specific place on the door, e.g. a bore in which the lock components are intended to be affixed, and where the robot with aid of a tool pulls the door towards itself and after painting also closes the door. A prerequisite for this opening and closing operation is that the car body is positioned rather accurately relative to the robot, which in turn means that the robot has to be so complex as to be able to make the rather complicated motion patterns required for the opening and closing. Robots of this type are very expensive and they furthermore take up a great deal of space.
The same or similar problems will arise during other operations in the car industry and also in other industries.
It is known from CH 534797 to open a door of a building with the aid of electromagnets, which are recessed in a door leaf and the magnet poles of which face the floor, where they cooperate with ferromagnetic blocks recessed in the floor. By activating the magnets successively with programming equipment a displacement is obtained between the blocks.